The present invention relates to internal combustion engines, and more particularly, but not exclusively, is directed to operating techniques for a turbocharged internal combustion engine to better accommodate load changes.
It is generally desirable that internal combustion engines rapidly respond to changing load conditions in as efficient a manner as possible. One application that commonly presents large, sudden load increases is a back-up power generation system having an internal combustion engine as the prime mover. Frequently, these arrangements are used to provide power to vital systems in the event of an unexpected loss of electric power from the usual sourcesxe2x80x94such as the power company grid. One difficulty with these arrangements is that the transition of the engine from a light stand-by generator load to a full generator load, sometimes called xe2x80x9cblock loading,xe2x80x9d causes a significant droop in the electrical output of the generator. This droop may be harmful to systems being provided the electric power.
One attempt to solve this problem has been to increase the size of the engine to handle block loading. However, once the block loading transition has passed, the engine is typically oversized in relation to the steady state loading imposed by the generator. Thus, there is a need for a more efficient technique to accept back-up generator loads without imposing a substantial transition droop penalty. Also, it would be particularly advantageous if this need could be met using an engine capable of operation with a gaseous fuel because of its ready availability in many locations that require a back-up power generation system. Moreover, other internal combustion engine applications would benefit from better techniques to handle load transitions, including, for example, vehicle applications.
The present invention meets these needs and provides other important benefits and advantages.
One form of the present invention is a unique internal combustion engine system. Additionally or alternatively, another form of the present invention includes a unique technique to handle engine load transitions. These forms may include skip fueling and/or controllably altering engine timing. Also, these forms may find use in a variety of internal combustion engine applications, including electric power generation, and vehicle propulsion systems, to name a few.
A further form of the present invention is a technique for generating electric power. This technique includes starting an internal combustion engine having a number of combustion chambers and a turbocharger. The engine is a primary source of motive power for an electric power generator. The chambers each have a respective fueling period. The engine is prepared to accept a generator load by withholding fuel during a respective fueling period of a portion of the chambers to increase boost pressure provided with the turbocharger.
In another form of the present invention, a technique for generating electric power includes starting an internal combustion engine that has a number of combustion chambers and a turbocharger. The engine is a prime mover for an electric power generator. The engine is prepared to accept a generator load by retarding ignition timing of at least a portion of the chambers to reach a predetermined boost pressure threshold with the turbocharger.
In still another form of the present invention, an engine includes a number of combustion chambers, a compressor along an intake pathway to deliver pressurized air to the chambers, and a turbine along an exhaust pathway to power the compressor. The system also has a means for preparing the engine to accept load transitions by providing a corresponding pressure level with the compressor. An engine crankshaft may be rotatably coupled to an electric power generator to provide an electric power generation system and correspondingly accommodate block loading with this means.
An additional form includes an electric power generation system having an electric power generator, an internal combustion engine, a sensor, and a controller. The engine includes a crankshaft rotatably coupled to the generator and a number of cylinders each having a reciprocating piston rotatably coupled to the crankshaft. The cylinders each correspond to one or more of a number of fuel injectors to be selectively fueled therewith during a respective fueling period. A compressor is provided along an intake pathway to deliver pressurized air to the cylinders and a turbine is provided along an exhaust pathway to power the compressor when driven by exhaust from the cylinders. The sensor provides a sensor signal corresponding to pressure provided by the compressor. The controller is operatively coupled to the injectors to regulate cylinder fueling and is responsive to the sensor signal to prepare the engine for a generator load increase. This preparation includes withholding fuel during a respective fueling period of a subset of the cylinders to increase the pressure provided by the compressor. Alternatively or additionally, such preparation may include retarding ignition in the cylinders. The form of ignition subject to retardation may be of any type, such as spark ignition or compression ignition. The controller generates a readiness signal when the pressure reaches a predetermined threshold. The engine accepts the generator load increase in response to the readiness signal.
Yet another form of the present invention is a system including an internal combustion engine, a sensor, and a controller. The engine includes a number of cylinders each having a reciprocating piston rotatably coupled to a crankshaft. The cylinders each have one or more fuel injectors to selectively provide fuel. The sensor provides a signal corresponding to a performance characteristic of the engine. The controller is responsive to the signal to provide skip-fueling of the engine. A quantity of skipped cylinders for a predetermined number of engine cycles is determined by the controller in accordance with the signal. The controller defines a number of skip-fueling patterns each corresponding to a different value of the quantity. The patterns each designate which of the cylinders are skipped and are each configured to rotate through a common number of configurations relative to a reference cylinder. This common number differs from the number of cylinders by at least one. The controller selects one of the patterns in accordance with the quantity and correspondingly generates one or more fuel injection signals when the engine is being skip-fueled. The injectors respond to such signals to fuel of the patterns.
Accordingly, it is one object of the present invention to provide an improved internal combustion engine.
Another object of the present invention is to improve management of changing engine loads.
It is still another object to prepare an internal combustion engine to accept a load increase presented by an electrical power generator.
Further forms, features, objects, advantages, benefits, and aspects of the present invention shall become apparent from the detailed description and drawings provided herewith.